Multi-zone resistive heater

1. An apparatus comprising: a stage comprising a surface having an area to support a wafer and a body; a shaft coupled to the stage; a first heating element disposed within a first plane of the body of the stage; and a second heating element disposed within a second plane of the body of the stage that is a greater distance from the surface of the stage than the first plane of the body, wherein the first heating element supplies a variable heat energy to an area of the surface of the stage.

2. The apparatus of claim 1 , wherein the first heating element occupies an area of the stage substantially the same size as an area of the stage occupied by the second heating element.

3. The apparatus of claim 1 , wherein the stage comprises a first surface to support a wafer and a second surface, and the shaft has a portion defining an interior opening through a length of the shaft, wherein the shaft is coupled to the second surface of the stage at a point substantially corresponding to the midpoint, and power leads to each of the first heating element and the second heating element are disposed in the opening.

4. The apparatus of claim 1 , wherein the stage body is substantially cylindrical such that a midpoint corresponds to an axis normal to the surface and a first portion of the area of the stage is defined by a first radius about the axis and a second portion of the area is defined by a second radius about the axis greater than the first radius.

5. The apparatus of claim 4 , wherein the first heating element is a resistive heating element comprising a first resistance in an area corresponding with the first portion of the area of the stage and a second resistance in an area corresponding with the second portion of the area of the stage, and wherein the second heating element is a resistive heating element comprising a first resistance in an area corresponding with the first portion of the area of the stage and a second resistance in an area corresponding with the second portion of the area of the stage.

6. The apparatus of claim 5 , wherein the first resistance of the first heating element is less than the second resistance of the first heating element and the first resistance of the second heating element is greater than the second resistance of the second heating element.

7. The apparatus of claim 4 , wherein the power density of the first heating element is greater than the power density of the second heating element in an area corresponding with the first portion of the area of the stage and the power density of the second heating element in an area corresponding with the second portion of the area of the stage.

8. The apparatus of claim 1 , wherein the first heating element is disposed about the first portion in a pair of coils and the first portion is defined by two segments separated by a first axis, a first coil disposed in a first segment of the first portion and a second coil disposed in a second segment of the first portion, the first coil coupled to the second coil through the first axis, wherein the second heating element is disposed about the second portion in a pair of coils and the second portion is defined by two segments separated by a second axis, a first coil disposed in a first segment of the second portion and a second coil disposed in a second segment of the second portion, the first coil coupled to the second coil through the second axis, and an intersection of the first axis and the second axis defines an angle in a plane of the surface between 0 and 180 .

9. The apparatus of claim 8 , wherein the stage body is substantially cylindrical such that a midpoint corresponds to an axis normal to the surface and a first portion of the area of the stage is defined by a first radius about the axis and a second portion of the area is defined by a second radius about the axis greater than the first radius, wherein the power density of the first heating element is greater than the power density of the second heating element in an area corresponding with the first portion of the area of the stage and the power density of the second heating element in an area corresponding with the second portion of the area of the stage.

10. The apparatus of claim 1 , wherein the stage is comprised of a material that is resilient to temperatures in excess of 750 C.

11. The apparatus of claim 10 , wherein the stage and the shaft are comprised of aluminum nitride.

12. The apparatus of claim 11 , wherein the stage is comprised of aluminum nitride and has a thermal conductivity in the range of 140 W/mK to 200 W/mK and the shaft is comprised of aluminum nitride and has a thermal conductivity in the range of 60 W/mK to 100 W/mK.

13. The apparatus of claim 1 , wherein the area to support a wafer includes a wafer pocket depressed in the surface of the stage and having sidewalls disposed at an angle of approximately 60 to 80 relative to a plane perpendicular to the surface of the stage.

14. An apparatus comprising: a stage comprising a surface having an area to support a wafer and a body; a shaft coupled to the stage; a first heating element disposed within a first plane of the body of the stage; and a second heating element disposed within a second plane of the body of the stage that is a greater distance from the surface of the stage than the first plane of the body, wherein the first heating element is a resistive heating element comprising a first portion having a first resistance and a second portion having a second resistance different than the first resistance.

15. The apparatus of claim 14 , wherein the second portion of the first heating element is disposed within an area of the stage at a greater distance from a midpoint of the area than the first portion of the first heating element.

16. The apparatus of claim 14 , wherein the second heating element is a resistive heating element comprising a first portion having a first resistance and a second portion having a second resistance different than the first resistance.

17. The apparatus of claim 16 , wherein the second portion of the second heating element is disposed within an area of the stage at a greater distance from a midpoint of the area than the first portion of the second heating element.

18. A reactor comprising: a chamber; and a resistive heater comprising a stage disposed within the chamber including a surface having an area to support a wafer and a body, a shaft coupled to the stage, a first heating element disposed within a first portion of the area of the stage and within a first plane of the body of the stage, and a second heating element disposed within a second portion of the area of the stage and in a second plane of the body of the stage, the second plane of the body of the heater is a greater distance from the surface of the stage than the first plane of the body, wherein a power density of the first heating element is greater than a power density of the second heating element in an area corresponding with a first portion of the stage area and the power density of the first heating element is less than the power density of the second heating element in an area corresponding with a second portion of the stage area.

19. The reactor of claim 18 , wherein the stage body is substantially cylindrical such that a midpoint corresponds to an axis normal to the surface and the second stage area is disposed at a greater distance from the midpoint than the first stage area.

20. The reactor of claim 18 , wherein the first heating element is disposed about the first portion in a pair of coils and the first portion is defined by two segments separated by a first axis, a first coil disposed in a first segment of the first portion and a second coil disposed in a second segment of the first portion, the first coil coupled to the second coil through the first axis, wherein the second heating element is disposed about the second portion in a pair of coils and the second portion is defined by two segments separated by a second axis, a first coil disposed in a first segment of the second portion and a second coil disposed in a second segment of the second portion, the first coil coupled to the second coil through the second axis, and an intersection of the first axis and the second axis defines an angle in a plane of the surface between 0 and 180 .

21. The reactor of claim 18 , further comprising: a first temperature sensor disposed within the shaft positioned to measure a first temperature of the stage; and a second temperature sensor positioned to measure a second temperature in an area of the stage corresponding to one of the first portion of the area of the stage and a second portion of the area of the stage.

22. The reactor of claim 21 , wherein the first temperature sensor is a thermocouple.

23. The reactor of claim 21 , wherein the second temperature sensor is a pyrometer.

24. The reactor of claim 23 , wherein the chamber comprises a top surface and the pyrometer is disposed in a window in the top surface of chamber.

25. The reactor of claim 18 , wherein the shaft has a portion defining an interior opening through a length of the shaft, the reactor further comprising a power source coupled to the first heating element and the second heating element through the opening in the shaft.

26. The reactor of claim 25 , further comprising a controller coupled to the power source to control the temperature of the first heating element and the second heating element.

27. The reactor of claim 26 , wherein the controller controls the temperature of the first heating element and the second heating element to within 3 C.

28. The reactor of claim 27 , wherein the controller is coupled to at least two of the first temperature sensor, and the second temperature sensor.

29. The reactor of claim 18 , wherein the heater is comprised of a material that is resilient to temperatures in excess of 750 C.

30. The reactor of claim 29 , wherein the stage is comprised of aluminum nitride and has a thermal conductivity in the range of 140 W/mK to 200 W/mK.

31. The reactor of claim 18 , wherein the body of the heater has a bottom surface and a portion defining an opening through the body and substantially normal to the surface, the reactor further comprising: a lift pin having a first end and a second end, the first end disposed within the opening through the body of the heater and the second end extending below the bottom surface of the body of the heater, a lifter assembly coupled to the shaft to move the heater between a first position and a second position within reactor chamber; and a lift plate coupled to the lifter assembly and having a portion disposed in the chamber, the portion disposed in the chamber including a surface extending in a direction normal to the shaft and substantially parallel to the top surface of the body of the stage, so that, when the heater is in the first position, the lift pin contacts the lift plate.

32. The reactor of claim 31 , wherein the lift plate is comprised of a material that is resilient to temperatures in excess of 750 C.

33. The reactor of claim 32 , wherein the lift plate is comprised of aluminum nitride and has a thermal conductivity in the range of 140 W/mK to 200 W/mK.

34. The reactor of claim 31 , wherein the lift pin is comprised of one of sapphire and aluminum nitride.

35. The reactor of claim 34 , wherein the opening through the body has a first portion having a first diameter to support a head of the lift pin and a second portion having a second diameter less than the first diameter.

36. The reactor of claim 18 , wherein the area to support a wafer includes a wafer pocket depressed in the surface of the stage and having sidewalls disposed at an angle of approximately 60 to 80 relative to a plane perpendicular to the surface of the stage.

37. A heating system for a chemical vapor deposition apparatus comprising: a resistive heater comprising a stage including a surface having an area to support a wafer and a body, a shaft coupled to the stage, a first heating element disposed within a first plane of the body of the stage, and a second heating element disposed within a second plane of the body of the stage, the second plane of the body of the stare is a greater distance from the surface of the stage than the first plane of the body; a first temperature sensor disposed within the shaft positioned to measure a first temperature of the stage; and a power source coupled to the first heating element and the second heating element.

38. The system of claim 37 , wherein a power density of the first heating element is greater than a power density of the second heating element in an area corresponding with the first portion of the area of the stage and the power density of the first heating element is less than power density of the second heating element in an area corresponding with the second portion of the area of the stage, wherein the stage body is substantially cylindrical such that a midpoint corresponds to an axis normal to the surface and a first portion of the area of the stage is defined by a first radius about the axis and a second portion of the area is defined by a second radius about the axis greater than the first radius.

39. The system of claim 38 , wherein the first heating element is disposed about the first portion in a pair of coils and the first portion is defined by two segments separated by a first axis, a first coil disposed in a first segment of the first portion and a second coil disposed in a second segment of the first portion, the first coil coupled to the second coil through the first axis, wherein the second heating element is disposed about the second portion in a pair of coils and the second portion is defined by two segments separated by a second axis, a first coil disposed in a first segment of the second portion and a second coil disposed in a second segment of the second portion, the first coil coupled to the second coil through the second axis, and an intersection of the first axis and the second axis defines an angle in a plane of the surface between 0 and 180 .

40. The system of claim 39 , wherein the intersection of the first axis and the second axis defines an angle in a plane of the surface of at least 90 .

41. The system of claim 38 , further comprising a second temperature sensor positioned to measure a second temperature corresponding to one of a first portion of the area of the stage and a second portion of the area of the stage and a third temperature sensor positioned to measure a third temperature in an area corresponding to the other of the first portion of the surface area of the stage and the second portion of the surface area of the stage.

42. The system of claim 38 , wherein the shaft of the heater has a portion defining an interior opening through a length of the shaft, the system further comprising a power source coupled to the first heating element and the second heating element through the opening in the shaft.

43. The system of claim 38 , further comprising a controller coupled to the power source to control the temperature of the first heating element and the second heating element.

44. The system of claim 43 , wherein the controller controls the temperature of the first heating element and the second heating element to within 2.5 C.

45. The system of claim 44 , wherein the controller is coupled to at least two of the first temperature sensor, the second temperature sensor, and the third temperature sensor.

46. The system of claim 45 , wherein the first temperature sensor is a thermocouple and the second temperature sensor and the third temperature sensor are each a pyrometer.

47. The system of claim 41 , wherein the second temperature sensor is disposed in a first window in the exterior surface of a chemical vapor deposition chamber and the third temperature sensor is disposed in a second window in the exterior surface of the chamber.

48. The system of claim 47 , further comprising a manifold coupled to the interior surface of the chamber to distribute process gases inside the chamber, the manifold positioned superiorly over the surface of the stage and having a thickness approximately three times the width of one of the first window and the second window.

49. The system of claim 37 , wherein the body of the heater has a bottom surface and a portion defining an opening through the body and substantially normal to the surface, the system further comprising: a lift pin having a first end and a second end, the first end disposed within the opening through the body of the heater and the second end extending below the bottom surface of the body of the heater, a lift assembly coupled to the shaft to move the heater between a first position and a second position within reactor chamber; and a lift plate coupled to the lift assembly and having a portion disposed in the chamber, the portion disposed in the chamber including a surface extending in a direction normal to the shaft and substantially parallel to the top surface of the body of the stage, so that, when the heater is in the first position, the lift pin contacts the lift plate.

50. The system of claim 49 , wherein the opening through the body has a first portion having a first diameter to support a head of the lift pin and a second portion having a second diameter less than the first diameter.

51. A method comprising: supplying a power to a first resistive heating element disposed within a first plane of the body of a stage of a resistive heater and a second resistive heating element disposed within a second plane of the body of the stage; and varying a resistance of at least one of the first resistive heating element and the second resistive heating element in at least two areas of the stage.

52. The method of claim 51 , wherein the step of varying a resistance of at least one of the first resistive heating element and the second resistive heating element comprises providing the at least one resistive heating element with a first portion having at least a first resistance and a second portion having at least a different second resistance.

53. The method of claim 51 , wherein the step of varying a resistance comprises varying a resistance of the first resistive heating element and a resistance of the second resistive heating element in at least two areas of the stage.

54. The method of claim 51 , wherein the resistive heater comprises a stage including a surface having an area to support a wafer and a body, the first heating element formed within a first plane of the body of the stage, and a second heating element formed within a second plane of the body of the stage, the second plane disposed at a greater distance from the surface area than the first heating element, the step of varying the resistance further comprising: with the first heating element, providing a greater resistance in an area of the stage defined by a first radius from a midpoint than a second area defined by a second radius from the midpoint greater than the first radius, and with the second heating element, providing a greater resistance in the second area than the first area.

55. The method of claim 51 , wherein the resistive heater comprises a stage including a surface having an area to support a wafer, the method further comprising: controlling the temperature of the surface of the stage by regulating the power supplied to the resistive heating elements.

56. The method of claim 55 , further comprising: measuring the temperature with at least two temperature sensors, a first temperature sensor disposed within a shaft extending from a bottom surface of the stage, the first temperature sensor positioned to measure a first temperature of the stage and a second temperature sensor positioned to measure a second temperature in a first area of the stage defined by a first radius from a midpoint and a second area defined by a second radius from the midpoint; and comparing the temperature measured by the first temperature sensor and the temperature measured by the second temperature sensor.

57. The method of claim 56 , wherein the step of controlling the temperature comprises controlling the compared temperature to within 2.5 C. at temperatures around 750 C.

58. A method comprising: providing a resistive heater in a chamber of a reactor, the resistive heater comprising a stage disposed within the chamber including a surface having an area to support a wafer and a body, a first heating element having a first power density and a second power density, the first heating element formed within a first plane of the body of the stage, and a second heating element having a first power density and a second power density, the second heating element formed within a second plane of the body of the stage, the second plane disposed at a greater distance from the surface than the first heating element; and supplying a power to the first heating element and to the second heating element.

59. The method of claim 58 , with the first heating element, providing a greater power density in an area of the stage defined by a first radius from a midpoint than a second area defined by a second radius from the midpoint greater than the first radius, and with the second heating element, providing a greater power density in the second area than the first area.

60. The method of claim 58 , further comprising: controlling the temperature of the surface of the stage by regulating the power supplied to the resistive heating elements.

61. The method of claim 60 , further comprising: measuring the temperature with at least two temperature sensors, a first temperature sensor disposed within a shaft extending from a bottom surface of the stage, the first temperature sensor positioned to measure a first temperature of the stage and a second temperature sensor positioned to measure a second temperature in a first area of the stage defined by a first radius from a midpoint and a second area defined by a second radius from the midpoint.

62. The method of claim 60 , the step of controlling the temperature further comprising controlling the temperature of the stage such that the second temperature measurement and the third temperature measurement are within 3 C. at temperatures around 750 C.